以主族元素为桥的梯形化合物的光电性质

梯形化合物具有大的平面π共轭结构, 不会产生构象扭曲, 可以有效增加π共轭长度, 因而表现出非常好的光电性质. 将主族元素引入到梯形化合物骨架中作为桥接单元不仅可以固定其结构而且由于主族元素和π共轭骨架之间的轨道相互作用, 可以实现对这类化合物光电性质的调节. 采用密度泛函理论对一系列主族元素桥的梯形化合物的结构和光电性质进行了理论研究, 从而可更好地理解和预测这类化合物的性质. 研究发现, 这类化合物的电子结构可以通过引入主族元素进行调节. 由于具有更大的π共轭程度, 四主族元素桥化合物的吸收与双主族元素桥化合物相比有明显的红移, 而且荧光寿命较短. 另外, 通过计算离子化势(IPs)、电子亲和能(EAs)和重组能(λ)考察了这类化合物的电子和空穴注入及传输性质. 研究发现, 四主族元素桥化合物表现出更强的电子和空穴注入能力.

Optoelectronic Properties for Main Group Element-Bridged Ladder Compounds

Ladder-type π-conjugated molecules with fully ring-fused structures have fascinating optoelectronic properties because the flattened π-conjugated framework can eliminate conformational disorder and effectively enhance π-conjugation. Their optoelectronic properties can be modified by incorporating main group elements into the ladder skeleton. Heteroatom-bridges not only stiffen the skeleton but also contribute to the electronic structure through orbital interaction between the main group elements and the π-conjugated skeleton. Herein, the structural, electronic, and optical properties of bisand tetrakis-bridged (C, Si or P-bridged) stilbene derivatives were investigated by density functional theory (DFT) and time-dependent DFT (TDDFT) to provide theoretical understanding and predictions for these compounds. The electronic structures of these π-conjugated skeletons could be tuned by the incorporated elements. Compared with bis-bridged analogs, tetrakis-bridged derivatives exhibited substantial red shifts in the absorption and shorter radiative lifetimes because of extended π-conjugation. In addition, the energy barrier for the injection and transport rates of the holes and electrons was evaluated using ionization potentials, electronic affinities, and reorganization energies (λ). Compared to bis-bridged analogs, tetrakis-bridged derivatives exhibit higher accepting abilities for both holes and electrons.